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Claunch NM, Nix E, Royal AE, Burgos LP, Corn M, DuBois PM, Ivey KN, King EC, Rucker KA, Shea TK, Stepanek J, Vansdadia S, Taylor EN. Body size impacts critical thermal maximum measurements in lizards. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 335:96-107. [PMID: 32851814 DOI: 10.1002/jez.2410] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 08/10/2020] [Accepted: 08/13/2020] [Indexed: 12/18/2022]
Abstract
Understanding the mechanisms behind critical thermal maxima (CTmax; the high body temperature at which neuromuscular coordination is lost) of organisms is central to understanding ectotherm thermal tolerance. Body size is an often overlooked variable that may affect interpretation of CTmax, and consequently, how CTmax is used to evaluate mechanistic hypotheses of thermal tolerance. We tested the hypothesis that body size affects CTmax and its interpretation in two experimental contexts. First, in four Sceloporus species, we examined how inter- and intraspecific variation in body size affected CTmax at normoxic and experimentally induced hypoxic conditions, and cloacal heating rate under normoxic conditions. Negative relationships between body size and CTmax were exaggerated in larger species, and hypoxia-related reductions in CTmax were unaffected by body size. Smaller individuals had faster cloacal heating rates and higher CTmax, and variation in cloacal heating rate affected CTmax in the largest species. Second, we examined how body size interacted with the location of body temperature measurements (i.e., cloaca vs. brain) in Sceloporus occidentalis, then compared this in living and deceased lizards. Brain temperatures were consistently lower than cloacal temperatures. Smaller lizards had larger brain-cloacal temperature differences than larger lizards, due to a slower cloacal heating rate in large lizards. Both live and dead lizards had lower brain than cloacal temperatures, suggesting living lizards do not actively maintain lower brain temperatures when they cannot pant. Thermal inertia influences CTmax data in complex ways, and body size should therefore be considered in studies involving CTmax data on species with variable sizes.
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Affiliation(s)
- Natalie M Claunch
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Emmeleia Nix
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Averil E Royal
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Luis P Burgos
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Megan Corn
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - P Mason DuBois
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Kathleen N Ivey
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Elina C King
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Kiley A Rucker
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Tanner K Shea
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - John Stepanek
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Sunny Vansdadia
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
| | - Emily N Taylor
- Biological Sciences, California Polytechnic State University, San Luis Obispo, California
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Barroso FM, Carretero MA, Silva F, Sannolo M. Assessing the reliability of thermography to infer internal body temperatures of lizards. J Therm Biol 2016; 62:90-96. [PMID: 27839556 DOI: 10.1016/j.jtherbio.2016.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 07/13/2016] [Accepted: 10/16/2016] [Indexed: 01/11/2023]
Abstract
For many years lizard thermal ecology studies have relied on the use of contact thermometry to obtain internal body temperature (Tb) of the animals. However, with progressing technology, an interest grew in using new, less invasive methods, such as InfraRed (IR) pyrometry and thermography, to infer Tb of reptiles. Nonetheless few studies have tested the reliability of these new tools. The present study tested the use of IR cameras as a non-invasive tool to infer Tb of lizards, using three differently body-sized lacertid species (Podarcis virescens, Lacerta schreiberi and Timon lepidus). Given the occurrence of regional heterothermy, we pairwise compared thermography readings of six body parts (snout, eye, head, dorsal, hind limb, tail base) to cloacal temperature (measured by a thermometer-associated thermocouple probe) commonly employed to measure Tb in field and lab studies. The results showed moderate to strong correlations (R2=0.84-0.99) between all body parts and cloacal temperature. However, despite the readings on the tail base showed the strongest correlation in all three species, it was the eye where the absolute values and pattern of temperature change most consistently followed the cloacal measurements. Hence, we concluded that the eye would be the body location whose IR camera readings more closely approximate that of the animal's internal environment. Alternatively, other body parts can be used, provided that a careful calibration is carried out. We provide guidelines for future research using thermography to infer Tb of lizards.
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Affiliation(s)
- Frederico M Barroso
- CIBIO, Research Centre in Biodiversity and Genetic Resources, InBIO, Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas, Vairão 4485-661, Vila do Conde, Portugal; College of Medical, Veterinary and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | - Miguel A Carretero
- CIBIO, Research Centre in Biodiversity and Genetic Resources, InBIO, Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas, Vairão 4485-661, Vila do Conde, Portugal
| | - Francisco Silva
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre, s/n, 4169-007, Porto, Portugal
| | - Marco Sannolo
- CIBIO, Research Centre in Biodiversity and Genetic Resources, InBIO, Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas, Vairão 4485-661, Vila do Conde, Portugal; Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre, s/n, 4169-007, Porto, Portugal.
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Fei T, Skidmore AK, Venus V, Wang T, Schlerf M, Toxopeus B, van Overjijk S, Bian M, Liu Y. A body temperature model for lizards as estimated from the thermal environment. J Therm Biol 2012. [DOI: 10.1016/j.jtherbio.2011.10.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Tosini G, Avery R. Intraspecific variation in lizard thermoregulatory set points: A thermographic study in Podarcis muralis. J Therm Biol 1993. [DOI: 10.1016/0306-4565(93)90037-t] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Trautwein SN, Gordon CJ, Heath JE. Changes in brain and body temperature of the lizard, Sceloporus undulatus hyacinthinus during rest and exercise. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0300-9629(85)90541-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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